In order to cut or drill brittle workpieces, such as stone, brick, concrete and asphalt, it is necessary to provide an abrasive material having hardness higher than that of the workpieces.
As for the abrasive material, synthetic diamond particles, natural diamond particles, nitrogen boride and cemented carbide are well known in the art, and particularly, the synthetic diamond particles have been most widely used in the art of cutting tools among these materials.
Synthetic diamond (referred to as “diamond” hereinafter) was invented in the 1950's, and is known to have a higher hardness than any other material on earth. Due to this property, diamond is widely used for cutting tools, grinding tools and the like.
Particularly, the diamond has been widely used in the field of stone machining when cutting or grinding a variety of stones, such as marble, granite and the like, and in the field of construction when cutting or grinding concrete structures.
A cutting segment (also referred to as “segment” hereinafter) comprising diamond particles as the abrasive material, and a cutting tool comprising the same will now be described.
Typically, a segment type diamond tool comprises a plurality of segments, each having diamond particles distributed thereon, and a steel core holding the segment.
FIG. 1 shows an example of the segment type diamond tool.
Referring to FIG. 1, the segment type diamond tool comprises a plurality of segments 11 and 12 fixed to a disk-shaped steel core 2 and having diamond particles 5 randomly distributed in each of the segments 11 and 12.
The segments are manufactured according to powder metallurgy, in which the diamond particles are mixed with metal powders acting as a matrix, and are then compacted and sintered.
As mentioned above, when the diamond particles are mixed with the metal powders, the diamond particles are not uniformly distributed among the metal powders, resulting in decreased cutting efficiency of the diamond particles and reduction in life span.
That is, when mixing the diamond particles and the metal powders acting as the matrix, differences in sizes and specific gravities between the particles cause segregation of the diamond particles, thereby generating non-uniform distribution of the diamond particles among the metal powders. As a result, as shown in FIG. 1, a cutting surface 3 in each segment with an excessively large amount of diamond particles distributed thereon or a cutting surface 4 with an excessively small amount of diamond particles distributed thereon can be formed.
When the diamond particles are segregated as described above, not only is the cutting efficiency of the cutting tool deteriorated, but the life span of the cutting tool is also reduced.
As a technology for solving the above problems caused by the segregation of the diamond particles, a patterning technology, which distributes the diamond particles in a predetermined pattern, is suggested and an example thereof is illustrated in FIG. 2.
FIG. 2 shows another example of a segment type diamond tool 20 in which the diamond particles are distributed in the predetermined pattern.
Referring to FIG. 2, each of the segments 21 and 22 has the diamond particles 5 distributed thereon in the predetermined pattern. That is, the diamond particles 5 are uniformly distributed in each of the segments 21 and 22.
According to a patterning technology, instead of mixing the metal powders and the diamond particles, the metal powders and the diamond particles are arranged in layers by repeating a process for arranging the diamond particles on the metal powder matrix in a predetermined pattern and a process for positioning the metal powder matrix on the diamond particles, and are then compacted into a predetermined compact, followed by sintering, thereby providing the segment.
Although the patterning technology for the diamond particles can solve the problems caused by the segregation of the diamond particles, intrinsic problems caused by the use of the powdered metal matrix cannot be solved.
That is, when manufacturing the segment, if the metal powders are used for the matrix, the metal powders are subjected to a higher pressure during a process of compacting the metal matrix. During the process of compacting the metal matrix, due to severe wear of a compaction die by the diamond particles, variation in the thickness of the matrix or breakage of the matrix frequently occurs, thereby lowering productivity. Furthermore, in severe cases, dimensions of the matrix are changed, so that the segments have different dimensions, respectively, resulting in performance variation and deterioration of the diamond tool.
Further, even though the metal powders for the matrix can be manufactured by various methods using the same components, manufacturing costs of the metal powders are remarkably high compared with a bulk of metal having a different shape, such as plate, coil, rod, and the like.
Additionally, when manufacturing the segments through powder metallurgy, a process for mixing the diamond particles and the metal powders, a process for compacting the mixture of the diamond particles and the metal powders into a predetermined compact, and a process for sintering the compact must be sequentially preformed, complicating the manufacturing processes.